HAL.Common 3.2.2

HAL

This project aims to bring a simple to use implementation of the Hypertext Application language.

Specification

• The formal specification is published as in IETF draft and can be found under https://tools.ietf.org/html/draft-kelly-json-hal-08.
• A more informal documentation can be found under http://stateless.co/hal_specification.html.

Usage

The project consists of three packages

1. HAL.Common which contains the IResource, IResource<T> and ILink implementations and the converters needed for serialization with System.Text.Json.
2. HAL.AspNetCore adds IResourceFactory and ILinkFactory which can be used in your controllers to easily generate resources from your models.
3. HAL.AspNetCore.OData adds IODataResourceFactory which can be used in your controllers to easily generate list endoints with paging from OData $skip and $top syntax.

Without OData support

In Startup.cs

public void ConfigureServices(IServiceCollection services)
{
   services
       .AddControllers() // or .AddMvc()
       .AddHal()
       .AddJsonOptions(o => // not neccessary, but creates a much nicer output
       {
           o.JsonSerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault; 
       });
}

In your controller

[Route("[controller]")]
public class MyController : HalControllerBase
{
   private readonly IResourceFactory _resourceFactory;

   public Table(IResourceFactory resourceFactory)
   {
       _resourceFactory = resourceFactory ?? throw new ArgumentNullException(nameof(resourceFactory));
   }

   [HttpGet]
   [ApiConventionMethod(typeof(DefaultApiConventions), nameof(DefaultApiConventions.Get))]
   public ActionResult<IResource> GetList()
   {
       var models = new[]
       {
           new MyModelListDto {Id = 1, Name = "Test1"},
           new MyModelListDto {Id = 2, Name = "Test2"},
       };

       var result = _resourceFactory.CreateForListEndpoint(models, _ => "items", m => m.Id);

       return Ok(result);
   }

   [HttpGet("{id}")]
   public ActionResult<IResource<ModelFullDto>> Get(int id)
   {
       var model = new ModelFullDto { Id = id, Name = $"Test{id}", Description = "Very important!" };

       var result = _resourceFactory.CreateForGetEndpoint(model);

       return Ok(result);
   }

   // PUT, POST, ...
}

With OData support

In Startup.cs

public void ConfigureServices(IServiceCollection services)
{
   services.AddOData();

   var modelBuilder = new ODataConventionModelBuilder();
   modelBuilder.EntitySet<MyModelListDto>(typeof(MyModelListDto).Name);
   services.AddSingleton(_ => modelBuilder.GetEdmModel());

   services
       .AddControllers() // or .AddMvc()
       .AddHALOData()
       .AddJsonOptions(o => // not neccessary, but creates a much nicer output
       {
           o.JsonSerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault; 
       });
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
   // ...

   app.UseEndpoints(endpoints =>
   {
       endpoints.MapControllers();
       endpoints.EnableDependencyInjection();  // Required for OData to work.
   });

   // ...
}

In your controller

[Route("[controller]")]
public class MyController : HalControllerBase
{
  private readonly IODataResourceFactory _resourceFactory;

  public Table(IODataResourceFactory resourceFactory)
  {
      _resourceFactory = resourceFactory ?? throw new ArgumentNullException(nameof(resourceFactory));
  }

  [HttpGet]
  [ApiConventionMethod(typeof(DefaultApiConventions), nameof(DefaultApiConventions.Get))]
  public ActionResult<Resource> GetList(
          // The SwaggerIgnore attribute and all parameters beside the options are just here to give you a nice swagger experience.
          // If you do not need that, you can remove everything except the options parameter.
          [SwaggerIgnore] ODataQueryOptions<TEntity> options,
          [FromQuery(Name = "$filter")] string? filter = default,
          [FromQuery(Name = "$orderby")] string? orderby = default,
          [FromQuery(Name = "$top")] long? top = default,
          [FromQuery(Name = "$skip")] long? skip = default)
  {
      var models = new[]
      {
          new MyModelListDto {Id = 1, Name = "Test1"},
          new MyModelListDto {Id = 2, Name = "Test2"},
      };

      // Apply the OData filtering
      models = options.Apply(models.AsQueryable()).Cast<MyModelListDto>().ToArray()

      var result = _resourceFactory.CreateForOdataListEndpointUsingSkipTopPaging(models, _ => "items", m => m.Id, options);

      return Ok(result);
  }

  // GET, PUT, POST, ...
}